<!DOCTYPE html>
<html lang="en-US">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <title>函数式编程 | 知识库演示</title>
    <meta name="generator" content="VuePress 1.9.9">
    <link rel="icon" href="/vdoing-demo-repository/img/favicon.ico">
    <meta name="description" content="web前端技术博客,简洁至上,专注web前端学习与总结。JavaScript,js,ES6,TypeScript,vue,python,css3,html5,Node,git,github等技术文章。">
    <meta name="keywords" content="前端博客,个人技术博客,前端,前端开发,前端框架,web前端,前端面试题,技术文档,学习,面试,JavaScript,js,ES6,TypeScript,vue,python,css3,html5,Node,git,github,markdown">
    <meta name="theme-color" content="#11a8cd">
    
    <link rel="preload" href="/vdoing-demo-repository/assets/css/0.styles.bb913129.css" as="style"><link rel="preload" href="/vdoing-demo-repository/assets/js/app.52e6b5d0.js" as="script"><link rel="preload" href="/vdoing-demo-repository/assets/js/2.f10ddeba.js" as="script"><link rel="preload" href="/vdoing-demo-repository/assets/js/115.96dc61ac.js" as="script"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/10.82e086d6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/100.2570dab9.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/101.b429c13f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/102.0e9afba4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/103.42e8d9d6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/104.6ca089b8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/105.f02335fc.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/106.2fe52c32.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/107.7650f18b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/108.7d825011.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/109.42092f8e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/11.49ec595f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/110.8e6f8d5b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/111.84bc1774.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/112.5da6cb16.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/113.2eb6714d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/114.dbdf6a79.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/116.2774e841.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/117.5a0ea935.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/118.72005b7a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/119.77fd4a33.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/12.66e2368f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/120.994b6190.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/121.794bec47.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/122.239044f6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/123.d6247b89.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/124.357cddf4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/125.b27c8c6b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/126.2f09d5b4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/127.5b5e7dcc.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/128.ca8342ed.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/129.62196c04.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/13.01d28bf6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/130.ae36e0a1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/131.63408c4f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/132.7a1bc472.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/133.6f365b21.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/134.7dfd70a1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/135.c110453c.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/136.dea9b77b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/137.212998a2.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/138.cf96d5b3.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/139.34437df0.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/14.52e25550.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/140.b28a1de4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/141.d117632d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/142.743bfbfc.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/143.d6c926e2.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/144.86916e4e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/145.a4658544.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/146.9f190393.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/147.b53beefe.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/148.d49c882d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/149.b5c8b142.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/15.ff9c9117.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/150.ab4902b7.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/151.aa13cf1a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/152.ca32ca39.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/153.f3dc7a9e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/154.2198d119.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/155.6cf21591.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/156.929b9e50.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/157.6d227e19.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/158.ad6e937f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/159.d74c55e1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/16.a59e9d0e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/160.1e9abdb1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/161.5343ce3e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/162.214b3f61.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/163.918d2361.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/164.204cab40.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/165.884ba632.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/166.e3bc3126.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/167.b8103188.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/168.176b21b8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/169.56e67ae6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/17.73f27920.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/170.05fe9454.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/171.ac72af48.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/172.134bd8be.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/173.f7b83d9b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/174.bc7aa46f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/175.c654668c.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/176.33b09327.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/177.97d7e55f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/178.ab02c611.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/179.0d88c6f5.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/18.39e882fe.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/180.1a2df1f3.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/181.533495f7.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/182.a4fc6807.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/183.e3a44f30.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/184.b731d331.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/185.e6eb67ad.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/186.c2493cb4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/187.279befae.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/188.1de7c987.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/189.e748958a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/19.ef7490a3.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/190.ad045bc8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/191.c3131762.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/192.29ea4e7e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/193.1e75aa14.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/194.f1150906.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/195.2a593c50.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/196.5aa5efe2.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/197.a328dc59.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/198.9db60424.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/199.d3b39a54.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/20.b5301937.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/200.a9dae555.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/21.2e9bd506.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/22.02e5e5a0.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/23.a00bf08d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/24.dae9e7bf.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/25.3120ccd4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/26.628f5a86.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/27.d4e86439.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/28.642a9f76.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/29.6c013ead.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/3.c3e96c9f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/30.4e45e23b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/31.9b0c4fcb.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/32.347f1a82.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/33.a17e9f72.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/34.ae475141.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/35.70d7eb87.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/36.0166a619.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/37.8d63783a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/38.91c94a9e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/39.edf5fef6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/4.f05e47c1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/40.f2dfda35.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/41.488faa5e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/42.258fde58.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/43.c46a30da.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/44.cfac4a51.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/45.58439e5f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/46.91d42cf4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/47.39ec1b7a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/48.900b1d2a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/49.4db4a295.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/5.85821e9b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/50.4a48e245.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/51.32253e74.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/52.f9692c89.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/53.f93fad53.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/54.cccf7ffb.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/55.7e4f324a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/56.5d04b9d7.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/57.ed34f737.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/58.9e762eed.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/59.81cfbcc1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/6.5f8d8bd6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/60.76f14de8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/61.a4d207e0.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/62.fce4471e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/63.58fd2153.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/64.b3f081c8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/65.dbde37b1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/66.49bc7970.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/67.48b689d5.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/68.a3660c81.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/69.b4057547.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/7.4acc3e20.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/70.5f3717cf.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/71.d47ff342.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/72.eca3c6ef.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/73.71bbaeec.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/74.6fe6e554.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/75.4dbad835.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/76.6ec52a3f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/77.9041350a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/78.e0b3aa97.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/79.1dbdb52c.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/8.503d9748.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/80.568b41f1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/81.9394cc64.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/82.e36a0a2e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/83.fba15f4a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/84.1a6a64b4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/85.af0f0d14.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/86.aed3f80d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/87.08c34bee.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/88.52b2750e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/89.6d27f363.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/9.9691b37e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/90.cccb0e61.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/91.6fb1e7f3.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/92.9e3d1d8a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/93.25bb0c7b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/94.0a896da5.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/95.41991c9b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/96.1f4103d8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/97.97ec058f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/98.f40afd31.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/99.ac67e72d.js">
    <link rel="stylesheet" href="/vdoing-demo-repository/assets/css/0.styles.bb913129.css">
  </head>
  <body class="theme-mode-light">
    <div id="app" data-server-rendered="true"><div class="theme-container sidebar-open have-rightmenu"><header class="navbar blur"><div title="目录" class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/vdoing-demo-repository/" class="home-link router-link-active"><img src="/vdoing-demo-repository/img/EB-logo.png" alt="知识库演示" class="logo"> <span class="site-name can-hide">知识库演示</span></a> <div class="links"><div class="search-box"><input aria-label="Search" autocomplete="off" spellcheck="false" value=""> <!----></div> <nav class="nav-links can-hide"><div class="nav-item"><a href="/vdoing-demo-repository/" class="nav-link">首页</a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="Python" class="dropdown-title"><a href="/vdoing-demo-repository/python/" class="link-title">Python</a> <span class="title" style="display:none;">Python</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>Python</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/c438df/" class="nav-link">Python基础</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="前端" class="dropdown-title"><a href="/vdoing-demo-repository/web/" class="link-title">前端</a> <span class="title" style="display:none;">前端</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>前端文章</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/8143cc480faf9a11/" class="nav-link">JavaScript</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/802a1ca6f7b71c59/" class="nav-link">Vue</a></li></ul></li><li class="dropdown-item"><h4>学习笔记</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/javascript/" class="nav-link">《JavaScript教程》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/es6/" class="nav-link">《ES6 教程》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/vue/" class="nav-link">《Vue》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/typescript-axios/" class="nav-link">《TypeScript 从零实现 axios》</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/wx-miniprogram/" class="nav-link">小程序笔记</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="页面" class="dropdown-title"><a href="/vdoing-demo-repository/ui/" class="link-title">页面</a> <span class="title" style="display:none;">页面</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/8309a5b876fc95e3/" class="nav-link">HTML</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/0a83b083bdf257cb/" class="nav-link">CSS</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="技术" class="dropdown-title"><a href="/vdoing-demo-repository/technology/" class="link-title">技术</a> <span class="title" style="display:none;">技术</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/9a7ee40fc232253e/" class="nav-link">技术文档</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/4c778760be26d8b3/" class="nav-link">GitHub技巧</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/117708e0af7f0bd9/" class="nav-link">Nodejs</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/41f87d890d0a02af/" class="nav-link">博客搭建</a></li></ul></div></div><div class="nav-item"><a href="/vdoing-demo-repository/archives/" class="nav-link">归档</a></div> <a href="https://github.com/xugaoyi/vuepress-theme-vdoing" target="_blank" rel="noopener noreferrer" class="repo-link">
    GitHub
    <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav></div></header> <div class="sidebar-mask"></div> <div class="sidebar-hover-trigger"></div> <aside class="sidebar" style="display:none;"><!----> <nav class="nav-links"><div class="nav-item"><a href="/vdoing-demo-repository/" class="nav-link">首页</a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="Python" class="dropdown-title"><a href="/vdoing-demo-repository/python/" class="link-title">Python</a> <span class="title" style="display:none;">Python</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>Python</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/c438df/" class="nav-link">Python基础</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="前端" class="dropdown-title"><a href="/vdoing-demo-repository/web/" class="link-title">前端</a> <span class="title" style="display:none;">前端</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>前端文章</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/8143cc480faf9a11/" class="nav-link">JavaScript</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/802a1ca6f7b71c59/" class="nav-link">Vue</a></li></ul></li><li class="dropdown-item"><h4>学习笔记</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/javascript/" class="nav-link">《JavaScript教程》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/es6/" class="nav-link">《ES6 教程》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/vue/" class="nav-link">《Vue》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/typescript-axios/" class="nav-link">《TypeScript 从零实现 axios》</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/wx-miniprogram/" class="nav-link">小程序笔记</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="页面" class="dropdown-title"><a href="/vdoing-demo-repository/ui/" class="link-title">页面</a> <span class="title" style="display:none;">页面</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/8309a5b876fc95e3/" class="nav-link">HTML</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/0a83b083bdf257cb/" class="nav-link">CSS</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="技术" class="dropdown-title"><a href="/vdoing-demo-repository/technology/" class="link-title">技术</a> <span class="title" style="display:none;">技术</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/9a7ee40fc232253e/" class="nav-link">技术文档</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/4c778760be26d8b3/" class="nav-link">GitHub技巧</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/117708e0af7f0bd9/" class="nav-link">Nodejs</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/41f87d890d0a02af/" class="nav-link">博客搭建</a></li></ul></div></div><div class="nav-item"><a href="/vdoing-demo-repository/archives/" class="nav-link">归档</a></div> <a href="https://github.com/xugaoyi/vuepress-theme-vdoing" target="_blank" rel="noopener noreferrer" class="repo-link">
    GitHub
    <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav>  <ul class="sidebar-links"><li><a href="/vdoing-demo-repository/pages/f344d070a1031ef7/" class="sidebar-link">ECMAScript 6 简介</a></li><li><a href="/vdoing-demo-repository/pages/c1edd70a6b7c7872/" class="sidebar-link">let 和 const 命令</a></li><li><a href="/vdoing-demo-repository/pages/b1ab10a62f7564da/" class="sidebar-link">变量的解构赋值</a></li><li><a href="/vdoing-demo-repository/pages/ca89eca8adeba5f4/" class="sidebar-link">字符串的扩展</a></li><li><a href="/vdoing-demo-repository/pages/a650b4a0ebfc9350/" class="sidebar-link">字符串的新增方法</a></li><li><a href="/vdoing-demo-repository/pages/0473261a6ab0ee8c/" class="sidebar-link">正则的扩展</a></li><li><a href="/vdoing-demo-repository/pages/5dfea9a0f2d1a392/" class="sidebar-link">数值的扩展</a></li><li><a href="/vdoing-demo-repository/pages/8ed309d668b20264/" class="sidebar-link">函数的扩展</a></li><li><a href="/vdoing-demo-repository/pages/e34009d60d8bc4b2/" class="sidebar-link">数组的扩展</a></li><li><a href="/vdoing-demo-repository/pages/b5e3e0a0ff6e9c25/" class="sidebar-link">对象的扩展</a></li><li><a href="/vdoing-demo-repository/pages/e85e68947502cf90/" class="sidebar-link">对象的新增方法</a></li><li><a href="/vdoing-demo-repository/pages/02c86eb2792f3262/" class="sidebar-link">Symbol</a></li><li><a href="/vdoing-demo-repository/pages/0c21dae358fca16b/" class="sidebar-link">Set 和 Map 数据结构</a></li><li><a href="/vdoing-demo-repository/pages/f56ec2ab97d60483/" class="sidebar-link">Proxy</a></li><li><a href="/vdoing-demo-repository/pages/74de3e45e4491e95/" class="sidebar-link">Reflect</a></li><li><a href="/vdoing-demo-repository/pages/2810ae8985e9bd52/" class="sidebar-link">Promise 对象</a></li><li><a href="/vdoing-demo-repository/pages/48df907ad3570f3d/" class="sidebar-link">Iterator 和 for-of 循环</a></li><li><a href="/vdoing-demo-repository/pages/718b48ed9ce0adce/" class="sidebar-link">Generator 函数的语法</a></li><li><a href="/vdoing-demo-repository/pages/75af7031eb66847b/" class="sidebar-link">Generator 函数的异步应用</a></li><li><a href="/vdoing-demo-repository/pages/3777253e65bac487/" class="sidebar-link">async 函数</a></li><li><a href="/vdoing-demo-repository/pages/e831e1593c82bbe0/" class="sidebar-link">Class 的基本语法</a></li><li><a href="/vdoing-demo-repository/pages/83f8c3a0cd87dd83/" class="sidebar-link">Class 的继承</a></li><li><a href="/vdoing-demo-repository/pages/efe2fb04eb8ac5fb/" class="sidebar-link">Module 的语法</a></li><li><a href="/vdoing-demo-repository/pages/a79ca2e64ceae213/" class="sidebar-link">Module 的加载实现</a></li><li><a href="/vdoing-demo-repository/pages/984bf549204bb266/" class="sidebar-link">编程风格</a></li><li><a href="/vdoing-demo-repository/pages/32c35f7651d6e58e/" class="sidebar-link">读懂 ECMAScript 规格</a></li><li><a href="/vdoing-demo-repository/pages/16121351be68691b/" class="sidebar-link">异步遍历器</a></li><li><a href="/vdoing-demo-repository/pages/a2ba314746bfdbdd/" class="sidebar-link">ArrayBuffer</a></li><li><a href="/vdoing-demo-repository/pages/7188882b8d65af1b/" class="sidebar-link">最新提案</a></li><li><a href="/vdoing-demo-repository/pages/e97bc1e5626b082c/" class="sidebar-link">装饰器</a></li><li><a href="/vdoing-demo-repository/pages/1cf50330655efc69/" aria-current="page" class="active sidebar-link">函数式编程</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/1cf50330655efc69/#柯里化" class="sidebar-link">柯里化</a></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/1cf50330655efc69/#函数合成" class="sidebar-link">函数合成</a></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/1cf50330655efc69/#参数倒置" class="sidebar-link">参数倒置</a></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/1cf50330655efc69/#执行边界" class="sidebar-link">执行边界</a></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/1cf50330655efc69/#队列操作" class="sidebar-link">队列操作</a></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/1cf50330655efc69/#合并操作" class="sidebar-link">合并操作</a></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/1cf50330655efc69/#配对操作" class="sidebar-link">配对操作</a></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/1cf50330655efc69/#参考链接" class="sidebar-link">参考链接</a></li></ul></li><li><a href="/vdoing-demo-repository/pages/6a8e2dc558da1b39/" class="sidebar-link">Mixin</a></li><li><a href="/vdoing-demo-repository/pages/8e8f80f69b775a56/" class="sidebar-link">SIMD</a></li><li><a href="/vdoing-demo-repository/pages/ea6f3b870f6dab69/" class="sidebar-link">参考链接</a></li></ul> </aside> <div><main class="page"><div class="theme-vdoing-wrapper "><div class="articleInfo-wrap" data-v-06225672><div class="articleInfo" data-v-06225672><ul class="breadcrumbs" data-v-06225672><li data-v-06225672><a href="/vdoing-demo-repository/" title="首页" class="iconfont icon-home router-link-active" data-v-06225672></a></li> <li data-v-06225672><a href="/vdoing-demo-repository/note/es6/#《ES6 教程》笔记" data-v-06225672>《ES6 教程》笔记</a></li></ul> <div class="info" data-v-06225672><div title="作者" class="author iconfont icon-touxiang" data-v-06225672><a href="javascript:;" data-v-06225672>阮一峰</a></div> <div title="创建时间" class="date iconfont icon-riqi" data-v-06225672><a href="javascript:;" data-v-06225672>2020-02-09</a></div> <!----></div></div></div> <!----> <div class="content-wrapper"><div class="right-menu-wrapper"><div class="right-menu-margin"><div class="right-menu-title">目录</div> <div class="right-menu-content"></div></div></div> <h1><img src="">函数式编程<!----></h1> <!----> <div class="theme-vdoing-content content__default"><h1 id="函数式编程"><a href="#函数式编程" class="header-anchor">#</a> 函数式编程</h1> <p>JavaScript 语言从一诞生，就具有函数式编程的烙印。它将函数作为一种独立的数据类型，与其他数据类型处于完全平等的地位。在 JavaScript 语言中，你可以采用面向对象编程，也可以采用函数式编程。有人甚至说，JavaScript 是有史以来第一种被大规模采用的函数式编程语言。

ES6 的种种新增功能，使得函数式编程变得更方便、更强大。本章介绍 ES6 如何进行函数式编程。</p> <h2 id="柯里化"><a href="#柯里化" class="header-anchor">#</a> 柯里化</h2> <p>柯里化（currying）指的是将一个多参数的函数拆分成一系列函数，每个拆分后的函数都只接受一个参数（unary）。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">function</span> <span class="token function">add</span> <span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">return</span> a <span class="token operator">+</span> b<span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token function">add</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token comment">// 2</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><p>上面代码中，函数<code>add</code>接受两个参数<code>a</code>和<code>b</code>。</p> <p>柯里化就是将上面的函数拆分成两个函数，每个函数都只接受一个参数。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">function</span> <span class="token function">add</span> <span class="token punctuation">(</span><span class="token parameter">a</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">return</span> <span class="token keyword">function</span> <span class="token punctuation">(</span><span class="token parameter">b</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> a <span class="token operator">+</span> b<span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token comment">// 或者采用箭头函数写法</span>
<span class="token keyword">const</span> <span class="token function-variable function">add</span> <span class="token operator">=</span> <span class="token parameter">x</span> <span class="token operator">=&gt;</span> <span class="token parameter">y</span> <span class="token operator">=&gt;</span> x <span class="token operator">+</span> y<span class="token punctuation">;</span>

<span class="token keyword">const</span> f <span class="token operator">=</span> <span class="token function">add</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">f</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span> <span class="token comment">// 2</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><p>上面代码中，函数<code>add</code>只接受一个参数<code>a</code>，返回一个函数<code>f</code>。函数<code>f</code>也只接受一个参数<code>b</code>。</p> <h2 id="函数合成"><a href="#函数合成" class="header-anchor">#</a> 函数合成</h2> <p>函数合成（function composition）指的是，将多个函数合成一个函数。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">const</span> <span class="token function-variable function">compose</span> <span class="token operator">=</span> <span class="token parameter">f</span> <span class="token operator">=&gt;</span> <span class="token parameter">g</span> <span class="token operator">=&gt;</span> <span class="token parameter">x</span> <span class="token operator">=&gt;</span> <span class="token function">f</span><span class="token punctuation">(</span><span class="token function">g</span><span class="token punctuation">(</span>x<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">const</span> f <span class="token operator">=</span> <span class="token function">compose</span> <span class="token punctuation">(</span><span class="token parameter">x</span> <span class="token operator">=&gt;</span> x <span class="token operator">*</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token punctuation">(</span><span class="token parameter">x</span> <span class="token operator">=&gt;</span> x <span class="token operator">+</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">f</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span> <span class="token comment">// 20</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><p>上面代码中，<code>compose</code>就是一个函数合成器，用于将两个函数合成一个函数。</p> <p>可以发现，柯里化与函数合成有着密切的联系。前者用于将一个函数拆成多个函数，后者用于将多个函数合并成一个函数。</p> <h2 id="参数倒置"><a href="#参数倒置" class="header-anchor">#</a> 参数倒置</h2> <p>参数倒置（flip）指的是改变函数前两个参数的顺序。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">var</span> <span class="token function-variable function">divide</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> a <span class="token operator">/</span> b<span class="token punctuation">;</span>
<span class="token keyword">var</span> flip <span class="token operator">=</span> f<span class="token punctuation">.</span><span class="token function">flip</span><span class="token punctuation">(</span>divide<span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token function">flip</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">)</span> <span class="token comment">// 0.5</span>
<span class="token function">flip</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">)</span> <span class="token comment">// 10</span>

<span class="token keyword">var</span> <span class="token function-variable function">three</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">[</span>a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">var</span> flip <span class="token operator">=</span> f<span class="token punctuation">.</span><span class="token function">flip</span><span class="token punctuation">(</span>three<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">flip</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// =&gt; [2, 1, 3]</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><p>上面代码中，如果按照正常的参数顺序，10 除以 5 等于 2。但是，参数倒置以后得到的新函数，结果就是 5 除以 10，结果得到 0.5。如果原函数有 3 个参数，则只颠倒前两个参数的位置。</p> <p>参数倒置的代码非常简单。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">let</span> f <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
f<span class="token punctuation">.</span><span class="token function-variable function">flip</span> <span class="token operator">=</span>
  <span class="token parameter">fn</span> <span class="token operator">=&gt;</span>
    <span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> <span class="token operator">...</span>args</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token function">fn</span><span class="token punctuation">(</span>b<span class="token punctuation">,</span> a<span class="token punctuation">,</span> <span class="token operator">...</span>args<span class="token punctuation">.</span><span class="token function">reverse</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h2 id="执行边界"><a href="#执行边界" class="header-anchor">#</a> 执行边界</h2> <p>执行边界（until）指的是函数执行到满足条件为止。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">let</span> <span class="token function-variable function">condition</span> <span class="token operator">=</span> <span class="token parameter">x</span> <span class="token operator">=&gt;</span> x <span class="token operator">&gt;</span> <span class="token number">100</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> <span class="token function-variable function">inc</span> <span class="token operator">=</span> <span class="token parameter">x</span> <span class="token operator">=&gt;</span> x <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> until <span class="token operator">=</span> f<span class="token punctuation">.</span><span class="token function">until</span><span class="token punctuation">(</span>condition<span class="token punctuation">,</span> inc<span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token function">until</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span> <span class="token comment">// 101</span>

<span class="token function-variable function">condition</span> <span class="token operator">=</span> <span class="token parameter">x</span> <span class="token operator">=&gt;</span> x <span class="token operator">===</span> <span class="token number">5</span><span class="token punctuation">;</span>
until <span class="token operator">=</span> f<span class="token punctuation">.</span><span class="token function">until</span><span class="token punctuation">(</span>condition<span class="token punctuation">,</span> inc<span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token function">until</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">)</span> <span class="token comment">// 5</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><p>上面代码中，第一段的条件是执行到<code>x</code>大于 100 为止，所以<code>x</code>初值为 0 时，会一直执行到 101。第二段的条件是执行到等于 5 为止，所以<code>x</code>最后的值是 5。</p> <p>执行边界的实现如下。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">let</span> f <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
f<span class="token punctuation">.</span><span class="token function-variable function">until</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter">condition<span class="token punctuation">,</span> f</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span>
  <span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>args</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    <span class="token keyword">var</span> r <span class="token operator">=</span> <span class="token function">f</span><span class="token punctuation">.</span><span class="token function">apply</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">,</span> args<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">return</span> <span class="token function">condition</span><span class="token punctuation">(</span>r<span class="token punctuation">)</span> <span class="token operator">?</span> r <span class="token operator">:</span> f<span class="token punctuation">.</span><span class="token function">until</span><span class="token punctuation">(</span>condition<span class="token punctuation">,</span> f<span class="token punctuation">)</span><span class="token punctuation">(</span>r<span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><p>上面代码的关键就是，如果满足条件就返回结果，否则不断递归执行。</p> <h2 id="队列操作"><a href="#队列操作" class="header-anchor">#</a> 队列操作</h2> <p>队列（list）操作包括以下几种。</p> <ul><li><code>head</code>： 取出队列的第一个非空成员。</li> <li><code>last</code>： 取出有限队列的最后一个非空成员。</li> <li><code>tail</code>： 取出除了“队列头”以外的其他非空成员。</li> <li><code>init</code>： 取出除了“队列尾”以外的其他非空成员。</li></ul> <p>下面是例子。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code>f<span class="token punctuation">.</span><span class="token function">head</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">27</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token comment">// 5</span>
f<span class="token punctuation">.</span><span class="token function">last</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">27</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token comment">// 1</span>
f<span class="token punctuation">.</span><span class="token function">tail</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">27</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token comment">// [27, 3, 1]</span>
f<span class="token punctuation">.</span><span class="token function">init</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">27</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token comment">// [5, 27, 3]</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><p>这些方法的实现如下。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">let</span> f <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
f<span class="token punctuation">.</span><span class="token function-variable function">head</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>xs</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> xs<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
f<span class="token punctuation">.</span><span class="token function-variable function">last</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>xs</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> xs<span class="token punctuation">.</span><span class="token function">slice</span><span class="token punctuation">(</span><span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
f<span class="token punctuation">.</span><span class="token function-variable function">tail</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>xs</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token class-name">Array</span><span class="token punctuation">.</span>prototype<span class="token punctuation">.</span><span class="token function">slice</span><span class="token punctuation">.</span><span class="token function">call</span><span class="token punctuation">(</span>xs<span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
f<span class="token punctuation">.</span><span class="token function-variable function">init</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>xs</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> xs<span class="token punctuation">.</span><span class="token function">slice</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><h2 id="合并操作"><a href="#合并操作" class="header-anchor">#</a> 合并操作</h2> <p>合并操作分为<code>concat</code>和<code>concatMap</code>两种。前者就是将多个数组合成一个，后者则是先处理一下参数，然后再将处理结果合成一个数组。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code>f<span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token number">5</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token number">27</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token comment">// [5, 27, 3]</span>
f<span class="token punctuation">.</span><span class="token function">concatMap</span><span class="token punctuation">(</span><span class="token parameter">x</span> <span class="token operator">=&gt;</span> <span class="token string">'hi '</span> <span class="token operator">+</span> x<span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">]</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span> <span class="token comment">// ['hi 1', 'hi 2', 'hi 3']</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><p>这两种方法的实现代码如下。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">let</span> f <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">;</span>
f<span class="token punctuation">.</span><span class="token function-variable function">concat</span> <span class="token operator">=</span>
  <span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>xs</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> xs<span class="token punctuation">.</span><span class="token function">reduce</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> a<span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span>b<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
f<span class="token punctuation">.</span><span class="token function-variable function">concatMap</span> <span class="token operator">=</span>
  <span class="token punctuation">(</span><span class="token parameter">f<span class="token punctuation">,</span> <span class="token operator">...</span>xs</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> f<span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span>xs<span class="token punctuation">.</span><span class="token function">map</span><span class="token punctuation">(</span>f<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><h2 id="配对操作"><a href="#配对操作" class="header-anchor">#</a> 配对操作</h2> <p>配对操作分为<code>zip</code>和<code>zipWith</code>两种方法。<code>zip</code>操作将两个队列的成员，一一配对，合成一个新的队列。如果两个队列不等长，较长的那个队列多出来的成员，会被忽略。<code>zipWith</code>操作的第一个参数是一个函数，然后会将后面的队列成员一一配对，输入该函数，返回值就组成一个新的队列。</p> <p>下面是例子。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">let</span> a <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> b <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> c <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">6</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">,</span> <span class="token number">8</span><span class="token punctuation">]</span><span class="token punctuation">;</span>

f<span class="token punctuation">.</span><span class="token function">zip</span><span class="token punctuation">(</span>a<span class="token punctuation">,</span> b<span class="token punctuation">)</span> <span class="token comment">// [[0, 3], [1, 4], [2, 5]]</span>
f<span class="token punctuation">.</span><span class="token function">zipWith</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> a <span class="token operator">+</span> b<span class="token punctuation">,</span> a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">)</span> <span class="token comment">// [9, 12, 15]</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><p>上面代码中，<code>zipWith</code>方法的第一个参数是一个求和函数，它将后面三个队列的成员，一一配对进行相加。</p> <p>这两个方法的实现如下。</p> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">let</span> f <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">;</span>

f<span class="token punctuation">.</span><span class="token function-variable function">zip</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter"><span class="token operator">...</span>xs</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  <span class="token keyword">let</span> r <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
  <span class="token keyword">let</span> nple <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
  <span class="token keyword">let</span> length <span class="token operator">=</span> Math<span class="token punctuation">.</span><span class="token function">min</span><span class="token punctuation">.</span><span class="token function">apply</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">,</span> xs<span class="token punctuation">.</span><span class="token function">map</span><span class="token punctuation">(</span><span class="token parameter">x</span> <span class="token operator">=&gt;</span> x<span class="token punctuation">.</span>length<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

  <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">var</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> i <span class="token operator">&lt;</span> length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    xs<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span>
      <span class="token parameter">x</span> <span class="token operator">=&gt;</span> nple<span class="token punctuation">.</span><span class="token function">push</span><span class="token punctuation">(</span>x<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span>
    <span class="token punctuation">)</span><span class="token punctuation">;</span>

    r<span class="token punctuation">.</span><span class="token function">push</span><span class="token punctuation">(</span>nple<span class="token punctuation">)</span><span class="token punctuation">;</span>
    nple <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>

  <span class="token keyword">return</span> r<span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>

f<span class="token punctuation">.</span><span class="token function-variable function">zipWith</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter">op<span class="token punctuation">,</span> <span class="token operator">...</span>xs</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span>
  f<span class="token punctuation">.</span><span class="token function">zip</span><span class="token punctuation">.</span><span class="token function">apply</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">,</span> xs<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">map</span><span class="token punctuation">(</span>
    <span class="token punctuation">(</span><span class="token parameter">x</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> x<span class="token punctuation">.</span><span class="token function">reduce</span><span class="token punctuation">(</span>op<span class="token punctuation">)</span>
  <span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br></div></div><h2 id="参考链接"><a href="#参考链接" class="header-anchor">#</a> 参考链接</h2> <ul><li>Mateo Gianolio, <a href="http://casualjavascript.com/?1" target="_blank" rel="noopener noreferrer">Haskell in ES6: Part 1<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li></ul></div></div> <!----> <div class="page-edit"><div class="edit-link"><a href="https://github.com/xugaoyi/vuepress-theme-vdoing/edit/master/docs/《ES6 教程》笔记/31.函数式编程.md" target="_blank" rel="noopener noreferrer">编辑</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <!----> <!----></div> <div class="page-nav-wapper"><div class="page-nav-centre-wrap"><a href="/vdoing-demo-repository/pages/e97bc1e5626b082c/" class="page-nav-centre page-nav-centre-prev"><div class="tooltip">装饰器</div></a> <a href="/vdoing-demo-repository/pages/6a8e2dc558da1b39/" class="page-nav-centre page-nav-centre-next"><div class="tooltip">Mixin</div></a></div> <div class="page-nav"><p class="inner"><span class="prev">
        ←
        <a href="/vdoing-demo-repository/pages/e97bc1e5626b082c/" class="prev">装饰器</a></span> <span class="next"><a href="/vdoing-demo-repository/pages/6a8e2dc558da1b39/">Mixin</a>→
      </span></p></div></div></div> <!----></main></div> <div class="footer"><!----> 
  Theme by
  <a href="https://github.com/xugaoyi/vuepress-theme-vdoing" target="_blank" title="本站主题">Vdoing</a> 
    | Copyright © 2019-2023
    <span>Evan Xu | MIT License</span></div> <div class="buttons"><div title="返回顶部" class="button blur go-to-top iconfont icon-fanhuidingbu" style="display:none;"></div> <div title="去评论" class="button blur go-to-comment iconfont icon-pinglun" style="display:none;"></div> <div title="主题模式" class="button blur theme-mode-but iconfont icon-zhuti"><ul class="select-box" style="display:none;"><li class="iconfont icon-zidong">
          跟随系统
        </li><li class="iconfont icon-rijianmoshi">
          浅色模式
        </li><li class="iconfont icon-yejianmoshi">
          深色模式
        </li><li class="iconfont icon-yuedu">
          阅读模式
        </li></ul></div></div> <!----> <!----> <!----></div><div class="global-ui"></div></div>
    <script src="/vdoing-demo-repository/assets/js/app.52e6b5d0.js" defer></script><script src="/vdoing-demo-repository/assets/js/2.f10ddeba.js" defer></script><script src="/vdoing-demo-repository/assets/js/115.96dc61ac.js" defer></script>
  </body>
</html>
